This invention relates generally to locking mechanisms for threaded components and, more particularly, to locking devices for threaded water supply fixtures.
There is often a safety requirement for threaded devices to be locked into an engaged position. For example, in the field of spas, hot tubs, and jetted bathtubs (all of which will be referred to as "tubs"), water is supplied through supply pipes to openings in the wall of a tub, and fittings are attached to the ends of the supply pipes. In a typical arrangement, the fixture includes a bushing or sleeve that is secured by screw threads or by adhesive in the wall opening, and the pipe is engaged with the bushing and secured to it. Then an appropriate insert is engaged in the bushing by means of screw threads. The insert contains a number of internal passages through which the water flows from the pool or spa, and serves as a drain cover, directing water to a circulating pump an filter.
There are typically two requirements imposed on such structures by plumbing codes or by good design practice. First the insert portion of the structure should be removable, for cleaning or replacement. Second, and most important from the standpoint of this invention, the threaded insert must incorporate some type of locking device to prevent its inadvertent removal.
Locking devices for components secured by screw threads are typically of two basic types. There are lock nuts or lock washers that engage the same threads as the component being secured, and there are locking screw that engage in a radial hole in one of the components and, when tightened, bear down on or through the body of the other component to prevent relative rotation of the components.
Lock nuts and washers are not suitable in the application described above, since the threads are not usually accessible when the insert is engaged in the bushing. The solution usually adopted is to use a radially oriented locking screw, accessed by screw driver through an opening in the threaded insert. The principal difficulty with this type of locking arrangement is that the locking screw may completely disengage from the structure and become lost or misplaced. This problem is particularly acute in the hot tub application, where small locking screws are frequently lost through drain openings in the tub. Replacements may not be readily available, and the completion of maintenance may be delayed or prevented.
Accordingly, there is a clear need for a different type of locking mechanism for components secured together by screw threads. Ideally, the locking mechanism should be self-contained in one or both of the threaded components, and should not be removable. Of course, the locking mechanism should also be simple and convenient to use. The present invention satisfies these requirements.